Reciprocating fluid pressure motor



May 3, 1955 F. G. scHwElsTHAL 3,707,456

RECIPROCATING FLUID PRESSURE MOTOR May 3, 1955 F. G. SCHWEISTHALRECIPROCATING FLUID PRESSURE MOTOR Filed Dec. 24. 1949 5 Sheets--ShemI 2@lunar/716,155.

May 3, 1955 F. G. scHwElsTHAL 2,707,456

RECIPROCATING FLUID PRESSURE MOTOR Filed Dec. 24, 1949 3 Sheats-Sheet 3United States Patent O 2,707,456 RECIPROCATING FLUID PRESSURE MOTORFrederick G. Schweisthal, Skokie, Ill., assignor to Stewart- WarnerCorporation, Chicago, Ill., a corporation of Virginia ApplicationDecember 24, 1949, Serial No. 134,983

3 Claims. (C1. 121-134) My invention relates generally to reciprocatingHuid pressure operated motors and more particularly to improved valvemechanisms for such motors.

In fluid pressure operated motors of the reciprocating type in which thelluid pressure is alternately supplied to the opposite ends of the motorcylinder through the `operation of a D slide valve, the speed ofoperation the ends of the cylinder without necessitating that it lowthrough the D slide valve mechanism.

It is therefore a primary object of my invention to provide an improvedfluid pressure operated reciprocating motor in which the back pressureon the air being exhausted from the ends of the inotor cylinder isreduced, and the efciency and speed of operation of the motor therebyincreased.

A further object is to provide an improved valve mechanism forreciprocating pneumatically operated motors.

Other objects will appear from the following description,` referencebeing had to the accompanying drawings, in which:

Fig. 1 is an elevation of the motor, a portion thereof being shown infragmentary section;

Fig. 2 is a central vertical sectional View of the motor;

Fig. 3 is an enlarged transverse sectional View taken on the line 3-3 ofFig. 1;

Fig. 4 is an enlarged sectional View -taken on the line 4--4 of Fig. 1;and

Fig. 5 is a fragmentary sectional View showing the detent means for theD slide valve operator.

The invention is illustrated as forming parl: of a lubricant pump havingan operating rod and a cylinder 12. The pump maybe of any desiredconstruction such as shown, for example, in the prior patent to E. W.Davis 2,406,747 or 2,060,180. The upper end of the operating rod 10forms the piston rod of the motor piston 14 which is reciprocable in acylinder 16 having heads 18 and 19 secured thereto by studs 20. A valvebody 22 is secured to the head 18 by `studs 24. The valve body has a rDslide valve seat `plate 26 secured thereto, said plate having ports 28,29 and 30 formed therein. The port 28 communicates with a T-shapedpassageway leading `to a check valve 34 which is held against a valveseat 36 by a light spring 38, the latter being held in place by aretainer pressed into the counterbored lower end of the passageway 32. Apassageway 42 in the head 18 registers with the lower end of thepassageway 32 and communicates, through a passageway 44 in ICC Ving to acheck valve 54 similar to the check valve 34 previously described. Thelower end of the passageway 52 is in registry with passageway 56 in thehead 58 communicating with the upper end of the cylinder bore 48. A Dslide valve 60 located in a valve chest 61 is reciprocable over the faceof the valve seat plate 26 and has a portion fitting loosely in achordal milled groove 62 formed in the valve operator sleeve 64 which ismounted for sliding movement in a bore 66 formed in the valve body 22.The upper end of the bore 66 is closed by a cap 63 secured to the valvebody by studs 70. The piston rod 10 has a long bore 72 formed therein,the upper end of which is closed by a fitting 74 forming part of thepiston 14 and through which projects valve stern 76 having a head 78 atthe lower end thereof. The upper end of the valve stem projects throughthe head 18 and has an enlarged diameter portion Sil which is guided inthe head 18, is sealed by a flanged washer 81, and projects into thebore 66 of the valve body 22.

The operator 64 has a central bore 82, the lower end of which has ashoulder 84 and the upper end of which has a sleeve S6 threaded therein.A pair fof Washers 88 and 39 are normally held in the positions shown inFig. 2 in engagement, respectively, with the shoulder S4 and the sleeve86 by a compressed coil spring 90. The upper end of the valve stem 76has a head 92 riveted or otherwise secured thereto.

As indicated in Figs. 1 and 5, spring pressed ball detents 94 cooperatewith grooves 96 and 97 formed in the operator 64 to hold the latter, andthus the D slide valve 60, in either of two operative positions.

From the foregoing it will be clear that when the piston 14 nears theupper end of its stroke, the bottom of the bore 72 will engage the head7S of the valve stem 76, and the enlarged diameter portion 81) of thevalve stem 76 will engage washer 88 and move the latter upwardly againstthe force of the spring until the force exerted through the spring 90 issuiicient to overcome the restraining force applied by the springpressed ball detents 94, or until a spacing sleeve 98 which surroundsthe valve stein 76 between the washers 38 and 39 engages the washer 89,whereupon the operator 64 will be snapped to its upper position by thespring 94B, thereby changing the position of the D slide valve 60, and,as will hereinafter appear, venting the lower end of the cylinder andsupplying air under pressure to the upper end of the cylinder to causethe piston 14 to commence its downward stroke.

Near the end of the downward stroke of the `piston the head 78 of thevalve stem 76 is engaged by the tting 74 and the spring 90 againcompressed. by downward movement of the washer 39 to overcome therestraining 'force of the spring pressed ball detents 94 and thereafterto cause the operator 64 to snap to its lowermost position in which itis shown in Fig. 2. Air under pressure is supplied to the valve chest orbore 66 through a suitable conduit 100 which is connected to `a supplytting 102 to which compressed air supply hose may be coupled.

Except for the provision of the check valves 34 and 54, the constructionof the motor and valve mechanism, as thus far described, issubstantially conventional. As best shown in Fig. l, the cylinder 16 isprovided with upper and lower relief valve bosses 104 `and 105 which maybe formed integrally with the cylinder 16. The relief valves in thesebosses are identical and only the lower relief valve contained in theboss 105, which is `shown in Fig. 4, will be described. The boss S isprovided with a passageway 106 which communicates with the lowerextremity of the motor cylinder bore 48. The boss 105 is provided withan exhaust port 109 and a counterbore 108, the end of the latter forminga seat 110 for a relief valve 112 which has a valve disc 114 securedthereon, and has a piston part 116 which is slidable in the counterbore108. A generally V-shaped packing ring 118 is loosely held between apair of washers 120 and 121. The valve disc 114 is held against the seat110 by a compressed relatively weak coil spring 124, which is seated ina bushing 126 threaded in the end of the counterbore 108. The bushing126 has a tube 128 (Fig. 1) suitably connected thereto, the upper end ofthe tube being secured in an elbow 130 which is threaded in one end ofthe T-shaped passageway 32, Similarly, a conduit 132 connects the reliefvalve boss 104 to a fitting 134 which is threaded into a passageway 136which is shown in phantom in Fig. 2 and communicates with the passageway52.

When the D valve 60 is in its lower position, as shown in Fig. 2, airunder pressure flows through port 28 and passageway 32, past check valve36 and passageways 42, 44 and 46 into the lower end of the motorcylinder bore 48. Air under pressure likewise flows through the conduit128 to the relief valve counterbore 108 and thus holds the valve disc114 against its seat, by virtue of the fact that the diameter of thepiston 116 is greater than that of the end of the passageway 106 whichis closed by the valve disc 114. At the same time the relief valve inthe boss 104 at the upper end of the cylinder is forced from its seat,against the slight force applied by its spring 124, and the air underpressure above the piston 114 is rapidly vented to the atmospherethrough its elbow shaped passageway 106 and its large exhaust port 138.This may take place because the conduit 132 is vented to the atmospherethrough the D slide valve 60 and exhaust port 50. At the opposite end ofthe stroke of the motor piston 14 the D slide valve 60 is shifted toconnect the conduit 128 to the exhaust port 50 and to permit air underpressure to flow from the valve chest 61 into the upper end of thecylinder through the passageway 52 and past check valve 54 while at thesame time supplying air under pressure to the conduit 132 and the reliefvalve contained in the boss 104 at the upper end of the cylinder 48. Therelief valve 112 in the boss 105 is thus free to open and permit thecompressed air beneath the piston 14 to escape freely to the atmospherethrough the associated passageway 106 and exhaust port 109.

It will be clear that by the use of the pressure relief valve 112, theoperation of which is controlled by the D slide valve 60, the end of thecylinder to which air under pressure is not being supplied, is rapidlyand efficiently vented to the atmosphere so that the back pressure onthe piston 14 is greatly reduced. lt will be understood that the springs124 of the relief valves are very light, being sufficient only toovercome the friction between the relief valves and the counterbores 108in which they reciprocate so that the relief valves do not impose anysubstantial restriction nor do they materially impede the free dischargeof air past them. Similarly, the check valves 34 and 54 are held againsttheir seats by the relatively weak springs 38 and thus do not impose anappreciable Vrestriction to the free flow of air past them.

While I have shown and described a preferred embodiment of my invention,it will be apparent that numerous variations and modifications thereofmay be made without departing from the underlying principles of theinvention, I therefore desire, by the following claims, to includewithin the scope of the invention all such variations and modificationsby which substantially the results of my invention may be obtainedthrough the use of substantially the same or equivalent means.

I claim:

l. In a compressed air operated motor, a motor cylinder, a pistonreciprocable therein, a D slide valve mechanism operated by the pistonalternately to admit air under pressure to the opposite ends of thecylinder, check valves to prevent return flow of air from the ends ofthe cylinder to the D slide valve mechanism, means forming a relief portat each end of the cylinder for freely exhausting air therefrom to theatmosphere, relief valves normally closing said relief ports, apneumatic operator for each of the relief valves operable when suppliedwith air under pressure to maintain the relief valve closed, and meansfor conveying air under pressure from the valve mechanism to thepneumatic operator associated with the relief valve at the end of thecylinder to which air under pressure is being supplied through the valvemechanism.

2. A compressed air operated motor comprising a cylinder, a pistonreciprocable in the cylinder, means forming passageways leading to theopposite ends of the cylinder, a Valve mechanism operated by the pistonat the ends of its stroke alternately to supply air under pressure tosaid passageways, a check valve in each of said passageways, an exhaustvalve at each end of the cylinder providing a relatively largev vent forthe discharge of air to the atmosphere, light springs biasing theexhaust valves to closed position, pneumatic motor devices connectedrespectively to the exhaust valves to hold the latter closed, and airconduits respectively connecting said passageways leading to the headend and rod end of the cylinder with the pneumatic motor devicesassociated with the exhaust valves at the head end and rod end of thecylinder, the connections of the conduits to the passageways being atthe inlet sides of the check valves in these passageways.

3. A valve apparatus for a fluid pressure operated reciprocating motorhaving a cylinder and a piston reciprocable in the cylinder, comprisingmeans forming an exhaust port and two passageways respectively connectedto the opposite ends of the cylinder, a two-position valve foralternately connecting one of the passageways to a source of fluid underpressure while connecting the other passageway to the exhaust port,check valve means respectively in said passageways for permittingv fiowof air under pressure toward the ends of the cylinder but preventingflow in the opposite direction, means operated by the piston forshifting the valve from one position to the other near the end of thepiston stroke, means forming a fluid pressure relief port at each end ofthe cylinder, a relief valve for each of said relief ports, a fluidpressure operated actuator for each of the relief valves operable toclose the valve when subjected to the motion of fiuid under pressure,means connecting the actuator for the relief valve at the head end ofthe cylinder to the passageway leading to the head end of the cylinder,and means connecting the actuator for the relief valve at the rod end ofthe cylinder to the passageway leading to the rod end of the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 37,186Walters Dec. 16, 1862 259,432 St. John lune 13, 1882 400,323 Gever Mar.26, 1889 417,329 Marsh, Jr. Dec. 17, 1889 554,364 Getty Feb. 11, 1896816,348 Miller Mar. 27, 1906 1,304,286 Emden May 20, 1919 1,348,672Wainwright Aug. 3, 1920

